1. Field of the Invention
The present invention relates to a drive apparatus for a writable recording medium and to a method of detecting the boundary between a recorded region and a recordable region on a recording medium.
2. Description of the Related Art
CD-R (Recordable) and CD-RW (CD-Rewritable) belong to both the CD-type disc and writable recording media families. CD-R is a write-once medium which uses an organic dye in the recording layer and CD-RW is a rewritable medium which uses a phase change technology. A drive apparatus (recording/reproducing apparatus) corresponding to CD-RW can erase recorded data and write new data to the erased region.
A CD-RW drive apparatus can perform data erasure by one of two methods: physical erasure and logical erasure. Physical erasure is a method in which data written on a disc is erased physically, thereby restoring the disc surface to a state where nothing is written. Logical erasure is a method in which particular information is overwritten into a subcode in the data. When read, this information indicates that the recorded data which still exists on the recording medium can be ignored.
When a disc is mounted, the drive apparatus needs to find the end (data end) of the portion of the disc where data is recorded. This data end corresponds to a boundary portion between a recorded region and a recordable region. The recordable region can be either a portion that has not previously been recorded on, a physically erased portion, or a logically erased portion.
When the boundary between a recorded region and a recordable region is found, the drive apparatus reports that fact to a host apparatus (e.g., a personal computer). Once a host apparatus recognizes a position (address) as a boundary on the disc, new data can be written to the disc starting from the boundary.
For example, assume that a certain data track was recorded on a disc as shown in FIG. 13(a) and logically erased as shown in FIG. 13(b), and that a new data track was thereafter recorded in the logically erased region as shown in FIG. 13(c). If the disc in the state of FIG. 13(c) is mounted in a drive apparatus, the drive apparatus detects the boundary shown in FIG. 13(c) and reports that fact to the host apparatus, whereby new data can be recorded in the region following the current data end.
However, correct detection cannot be performed when a logically erased region has not been re-recorded.
As shown in FIG. 14(a), a data end is a boundary between a recorded region and a region that has not previously been subjected to recording or is a physically erased region. To detect the boundary location, a drive apparatus performs a reproducing operation over the recorded region of a disc. An RF signal is returned from those regions which are recorded. Therefore, the boundary location is the position starting where no reproduction RF signal is returned.
However, in the case where, as shown in FIG. 14(b), a data end is a boundary with a logically erased region, this technique cannot be used to determine the boundary. This is because the data still exists in the logically erased region and hence a reproduction RF signal is returned by that region.
Because of this problem, the boundary with a logically erased region is normally determined using a subcode CRC error check.
As described later in detail, CD-RW data is written on a packet-by-packet basis and each packet is formed by a plurality of blocks. The head block of each packet is designated a link block. A link block is formed after the last packet in a packet-by-packet recording operation. FIG. 14(c) is an enlarged version of the boundary portion shown in FIG. 14(b) that is formed by such a recording operation. Each block is denoted as BL(n), BL(nxe2x88x921), . . .
A block which contains the write end point is made a link block. This link block, (i.e., a block where a physical writing operation was finished) includes logically erased data as shown in FIG. 14(c). Therefore, a subcode CRC check on this block necessarily results in an error.
Based on this fact, the drive apparatus performs a reproducing operation on a recorded region and determines in which blocks CRC errors occur. This makes it possible to detect, for example, block BL(n) shown in FIG. 14(c) as a boundary. However, this method of detection requires that no CRC errors occur in other blocks.
If for some reason such as a stain on the disc or data deterioration due to repetition of recording operations, a CRC error occurs at a block that is not a boundary, the drive apparatus may erroneously detect a boundary or fail to identify a boundary. For example, if a CRC error occurs at a non-boundary block such as block BL(nxe2x88x921) in addition to block BL(n) shown in FIG. 14(c), it cannot be determined which block is a true boundary. Since a boundary cannot be correctly detected in this manner, the reliability of the apparatus is lowered.
In view of the above problem, an object of the present invention is to correctly detect the boundary between a recorded region and a recordable region on a recording medium in a drive apparatus.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification and the drawings.
To attain the above objective, the invention provides a drive apparatus capable of recording or reproducing data on or from a recording medium in which each packet is formed by a plurality of blocks and on which data recording is performed on a packet-by-packet basis, the drive apparatus comprising a boundary detector for performing data reading on the recording medium in a state that data is recorded on the recording medium in the form of one or a plurality of packets having a particular packet length, and for determining a block where a reading error has occurred and that is located at a position distant from a track head by an integral multiple of the particular packet length as a boundary between a data-recorded region and a writable region. Thus, the invention makes it possible to correctly detect a boundary by using the fixed packet length in addition to detected reading errors as detection criteria.
The invention also provides a drive apparatus capable of recording or reproducing data on or from a recording medium on which data recording is performed on a packet-by-packet basis, each packet being prescribed so as to be formed by a plurality of blocks and include a particular type of block at least as an end block, the drive apparatus comprising a boundary detector for performing data reading on the recording medium in a state that data is recorded on the recording medium in the form of one or a plurality of packets, and for determining a boundary between a data-recorded region and a writable region by using a block reading error state and a block type as criteria. Thus, the invention makes it possible to correctly detect a boundary by using a block""s type in addition to a detected reading error as detection criteria.